A family from a village in Pakistan traveled all the way to Capitol Hill this week to tell lawmakers the story of how they lost their grandmother in a deadly attack. She was killed by a U.S. drone strike one year ago. Speaking through an interpreter, her grandchildren's testimony, along with that of her son, marked the first time civilians victimized by drone strikes appeared at a congressional briefing.

As NPR's Carrie Johnson reports, the episode put a human face on a policy that's grown more controversial at home and abroad.

CARRIE JOHNSON, BYLINE: Nine-year-old Nabila Rehman and her older brother Zubair say they were picking okra with their grandmother to get ready for the Eid holiday last October. Their home is in North Waziristan, a remote part of Pakistan. Then, around 3 P.M., Zubair says, the clear, blue skies darkened overhead.

ZUBAIR REHMAN: (Through translator) When the drone fired the first time, the whole ground shook, and black smoke rose up.

JOHNSON: The children ran before the second missile came down, but their grandmother never got up. She was the thread that held their family together, and she was gone. Little Nabila had a wound to her hand that wouldn't stop bleeding. And Zubair needed two surgeries to remove shrapnel from his legs.

REHMAN: (Through translator) I know Americans think drones are the answer, but I wish they could understand how I and other children in my community see drones.

JOHNSON: Zubair says he doesn't play soccer or cricket outdoors with his cousins anymore because they're too scared. His father, a primary school teacher named Rafiq ur Rehman told lawmakers that he worries, too.

RAFIQ UR REHMAN: (Through translator) As a teacher, my job is to educate. But how do I teach something like this? How do I explain what I myself do not understand? How can I, in good faith, reassure the children that the drone will not come back and kill them, too?

JOHNSON: The Rehman family came to Washington with the help of filmmaker Robert Greenwald, whose new documentary, called "Unmanned: America's Drone Wars," features them and other victims in Pakistan.

ROBERT GREENWALD: Almost everybody I talk to, at the end of the interview - and remember, these are people who had relatives killed by American policy - probably 60, 70 percent of them, at the end of the interview, would turned to me and say: Could you please tell President Obama that I'm not a terrorist?

JOHNSON: The Rehman family say they don't know why they were targeted. Their grandmother, they say, was not a militant. With the help of lawyers, they asked the government in Pakistan for answers. Eventually, they say, they got a letter in return, informing them the U.S. is responsible. That's why Rafiq bundled his children on an airplane and journeyed thousands of miles to Washington to appear at the briefing. It was sponsored by Florida Democratic Representative Alan Grayson.

REPRESENTATIVE ALAN GRAYSON: There needs to be increased oversight of the decisions to fly lethal weapons over another nation and kill people. And we should never accept that children and other loved ones in a faraway land are acceptable collateral damage.

JOHNSON: Grayson and four other Democrats in the U.S. House called on President Obama to release more facts about the drone strikes, and to explain his legal rationale for pursuing them. But just last week, the White House showed little sign it would back away from using drones altogether.

Spokesman Jay Carney said those weapons are the most precise way to go after militants who can't be captured. And he said drones kill far fewer innocent civilians than other methods for waging war.

Human rights lawyer Jennifer Gibson has been working with the Rehmans.

JENNIFER GIBSON: Drones defenders often claim that strikes are more precise than the alternative. But that precision is based on intelligence that we are finding time and time again to be false.

JOHNSON: Gibson says the Rehmans are not alone. Over the years, she's talked with more than 100 families who also lost loved ones to drones.